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Pot. Linear V with
RCB200
(position B) - Autoranging performances
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Files:
RCB200-B .EXP
RCB200-B 005.CRV
Abstract
A Pot. Linear Voltammetry establishes that the
autoranging is functioning according to the specifications. The
measurements are operated with autoranging up to 10 mA. The autoranging
from 100µA to 1 mA and from 1 mA to 10 mA are examined. The experiment
uses the "Auto Auto Auto" settings. Different settings are available
for the autoranging in current. You are invited to use "Auto Auto
Auto" mode by default. With this setting, no risk of range beating
and no risk of range overload. Maximum range=Auto, Minimum range=Auto
and Filter=Auto. This combination optimises the performances of
your equipment.
Sample
RCB200 with WORK connected to position B and
functional ground connected to the potentiostat rear panel.
Settings - Experimental
The linear voltammetry is operated at 10
mV/sec. The digital ramp has 500µV resolution. One point is recorded
every 8*0.25 = 2mV. The benefit is that the digital ramp is very
precise and the experimental file is not larger than needed.
Curve examination
Display: Type = Normal X = Current Y1 =
Potential Y2 = No
A simple way to evaluate the quality of
the measurement is to operate a linear regression on selected sections
of the experimental file. The slopes can be compared to the value
of the resistor and the accuracy of the measurement can be checked
with the offset (constant term).
Range 10mA
Linear regression----------------------- 02-09-1999, 15:15:11
X min.: 1
X max.: 3.304
Mode: y=f(x)
Result: y(V) = 1.209*x(mA/cm²) + 0.006
x(y=0) = -0.00430288
Coefficient: 0.999998
Range 1 mA
Linear regression----------------------- 02-09-1999, 15:30:03
X min. : 0.132
X max. : 0.836
Mode: y=f(x)
Result: y(V) = 1.208*x(mA/cm²) -0.001
x(y=0) = 0.000860909
Coefficient: 0.999999
1) Slope:
linearity of the range and determination of the value
The slope must be equal to the value of the resistance =1210 Ohms
±1%. The values must be comprised between 1200 and 1220 Ohms. This
is the case. Note that the difference between 1208 and 1209 is less
than 1/1000.
2) Offset:
Value at the origin [x(y=0)]
With range 10 mA [x(y=0) = -0.00430288 mA] can be compared
with the accuracy [0.2% of 10 mA = 0.02 mA]
With range 1 mA [ x(y=0) = 0.000860909 mA] can be compared
with the accuracy [0.2% of 1 mA = 0.002 mA]
However, what is important is that both ranges overlap with each
other. The difference between these offsets must be less than [0.02 mA
+ 0.002 mA = 0.022] to establish that both ranges are in accordance
with each other. This is the case since [0.000860909 - (-0.00430288
) = 0.005163 mA] is inferior to 0.022 mA.
Conclusion
The measurements are within specifications.
References and notes
You can evaluate the performances regarding the
resolution and the accuracy with the other ranges using the same
principle.
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